Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations ov...Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point.Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector(EFD) onboard the ZhangHeng-1 satellite(ZH-1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF(DC–16 Hz), ELF(6 Hz–2.2 kHz), VLF(1.8 kHz–20 kHz) and HF(18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1μV·m-1·Hz-1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m-1·Hz-1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m-1·Hz-1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m-1·Hz-1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH-1 is also introduced in this paper. During the six months' orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH-1 and is meeting the requirements of the scientific objectives of ZH-1.展开更多
亚洲表面贴装技术和电子制造行业盛会——NEPCON China 2015(NEPCON中国电子展)将于2015年4月21至23日在上海世博展览馆举办,展会涵盖:SMT表面贴装技术、表面焊接技术、电子测量测试、电子制造自动化、防静电等相关技术和产品。全新自...亚洲表面贴装技术和电子制造行业盛会——NEPCON China 2015(NEPCON中国电子展)将于2015年4月21至23日在上海世博展览馆举办,展会涵盖:SMT表面贴装技术、表面焊接技术、电子测量测试、电子制造自动化、防静电等相关技术和产品。全新自动流体点胶系统供应商——诺信EFD届时将在2015NEPCON中国电子展向业内同仁展示其全新P RO系列视觉导引自动点胶解决方案。展开更多
Three-dimensional(3-D)power prediction method from model test has been widely accepted and used for many years.Form factor k is the most important characteristics of 3・D method and very crucial to the accurate power p...Three-dimensional(3-D)power prediction method from model test has been widely accepted and used for many years.Form factor k is the most important characteristics of 3・D method and very crucial to the accurate power prediction.However,it's rather difficult to get the accurate value of k for those ships with pronounced bulbous or large transom from model test.In this paper,a new method to predict power is proposed,using k from CFD while other data from model test(or experimental fluid dynamics(EFD)).Delivered power prediction using the combination of CFD/EFD method agrees well with sea-trial results.展开更多
基金supported by the civil space research project (ZH-1 data validation: Ionospheric observatory theory)NFSC grants 41574139 and 41874174
文摘Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point.Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector(EFD) onboard the ZhangHeng-1 satellite(ZH-1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF(DC–16 Hz), ELF(6 Hz–2.2 kHz), VLF(1.8 kHz–20 kHz) and HF(18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1μV·m-1·Hz-1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m-1·Hz-1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m-1·Hz-1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m-1·Hz-1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH-1 is also introduced in this paper. During the six months' orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH-1 and is meeting the requirements of the scientific objectives of ZH-1.
文摘亚洲表面贴装技术和电子制造行业盛会——NEPCON China 2015(NEPCON中国电子展)将于2015年4月21至23日在上海世博展览馆举办,展会涵盖:SMT表面贴装技术、表面焊接技术、电子测量测试、电子制造自动化、防静电等相关技术和产品。全新自动流体点胶系统供应商——诺信EFD届时将在2015NEPCON中国电子展向业内同仁展示其全新P RO系列视觉导引自动点胶解决方案。
文摘Three-dimensional(3-D)power prediction method from model test has been widely accepted and used for many years.Form factor k is the most important characteristics of 3・D method and very crucial to the accurate power prediction.However,it's rather difficult to get the accurate value of k for those ships with pronounced bulbous or large transom from model test.In this paper,a new method to predict power is proposed,using k from CFD while other data from model test(or experimental fluid dynamics(EFD)).Delivered power prediction using the combination of CFD/EFD method agrees well with sea-trial results.
文摘针对经验傅里叶分解(empirical Fourier decomposition,EFD)在分析电能质量扰动时,其频带分割不具自适应的问题,提出了一种改进的EFD方法。首先,利用分段3次Hermite插值提取扰动信号归一化频谱的极大值包络,然后再搜索该包络的极大值,并计算其动态测度,将动态测度大于设定阈值的频率作为扰动信号的特征频率,以相邻特征频率的中点作为扰动信号频带分割的边界;其次,对分割的频带进行快速傅里叶逆变换(inverse fast Fourier transform,IFFT),得到对应频带的解析傅里叶固有频带函数(analytic Fourier intrinsic band function,AFIBF);最后,对分解出的各AFIBF分量进行Hilbert变换,提取出其扰动参数。通过对模拟信号和实测数据的分析,验证了所提方法的正确性和有效性。
